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Energy can be converted to other forms,
which can be stored for use.
When Earth's first plants appeared in our oceans there was no food for them, but living things
need food to stay alive. How did they survive?
The answer
is... they used sunlight
energy to make their own food!
All green plants on Earth today still do this. But how? In our air is a gas called carbon dioxide. Carbon dioxide molecules are made up of one carbon atom joined with two oxygen atoms. Using the energy from sunlight, green plants can break a carbon dioxide molecule, keeping the carbon atom and letting the two oxygen atoms go. They then use water and a green chemical in their leaves called chlorophyll to convert the collected carbon atoms into sugars which they store in their leaves, stems and branches. Those sugars are energy stores which the plants use to grow bigger and stay alive. Using sunlight
energy to turn carbon atoms
into food energy, is called photosynthesis. Photosynthesis was the
first way a living thing used energy. It paved the way for animals
to develop, because the energy in plants could be food for the animals.
How did people first use energy? |